Many current next-generation sequencing (NGS) platforms require special DNA and RNA preparations prior to sequencing. Most commonly used preparations involve addition of adaptor sequences to the ends of double-stranded DNA fragments through a ligation reaction. The reaction typically involves blunt-ended DNA or DNA with a single deoxyadenosine (dA) nucleotide at the 3′ end and a high concentration of DNA ligase, and the reaction results in formation of a significant number of chimeric templates. Template-independent polymerases such as DNA-specific terminal deoxynucleotidyl transferase (TdT), and RNA-specific poly(A) and poly(U) polymerases potentially represent an attractive alternative approach for preparation of DNA and RNA for NGS analysis with the challenging caveat that the length of polymeric tails produced by these enzymes varies in a wide range (from 20 to 500 nucleotides), depends on many factors, and is not easy to control, thus reducing their utility for NGS.